Inject Build Variables into the Manifest

If you need to insert variables into your AndroidManifest.xml file that are
defined in your build.gradle file, you can do so with the
manifestPlaceholders
property. This property takes a map of key-value pairs, as shown here:

By default, the build tools also provide your app's
application ID in the
${applicationId} placeholder. The value always matches the final application
ID for the current build (including
changes by build variants.
This is useful when you want to use a unique namespace for identifiers
such as an intent action, even between your build variants.